1. Field of the Invention
The present invention relates to a control device of switching devices, and more particularly to a control device of switching devices including a snubber circuit for suppressing a surge voltage.
2. Description of the Background Art
Power convertors such as inverters use a power MOSFET, an IGBT (Insulated Gate Bipolar Transistor) or the like as switching devices. Suppression of a surge voltage at switching time and power loss reduction present important problems in those switching devices.
For example, Japanese Patent Application Laid-Open No. 2001-217697 (FIG. 1) discloses a driving device of a semiconductor device which, by connecting two resistance variable means to a gate of a switching device a surge voltage of which should be suppressed, dividing a control voltage and applying it to the switching device as a gate voltage, suppresses a temporal variation in the gate voltage to suppress the surge voltage at switching time.
The driving device of the semiconductor device disclosed in the Japanese Patent Application Laid-Open No. 2001-217697 is configured with no consideration given to a snubber circuit. The addition of a snubber circuit to that configuration may result in an increase in the surge voltage or an increase in power loss in case a malfunction occurs in the snubber circuit. When it is used to control a motor of a hybrid car (a car using a motor and an engine as a power source), for example, the driving device may interfere with the car's drive in case a malfunction occurs in the snubber circuit.